Radiotherapy and chemotherapy are well-established treatment methods for malignant disease. Cells, which grow and divide rapidly, are most vulnerable to the effects of radiation and cytotoxic agents. Among those effected are tumor cells, and normal cells including hair and intestinal cells, and cells of the hemopoietic and immune systems. Damage to normal cells of the hemopoietic and immune systems by radiation and cytotoxic agents often has life-threatening consequences, and it limits the ability to administer a full therapeutic dose.
There has been extensive research to identify agents which will protect normal hemopoietic and immunologic cells from the effects of radiotherapy and chemotherapy, or aid in the reconstitution of cells suppressed by these therapies. For example, transforming growth factor beta-1 has been reported to be useful for protecting hematopoietic stem cells from the myelotoxicity of chemotherapeutic drugs or radiation therapy (U.S. Pat. No. 5,278,145 to Keller et al.) A lyophilised composition containing human albumin in thymosin alpha 1 was also reported to exert a preventative activity against progression of leukaemia's in mice whose immune systems were severely damaged by treatment with cytostatic agents or radiation treatment (89EP 102569 to Lattanzi). Hemopoietic growth factors such as interleukin-3 and CSF have been used to potentiate immune response or assist in reconstituting normal blood following radiation-or-chemotherapy-induced hematopoietic cell suppression (WO8805469 to Anderson et al., U.S. Pat. No. 4,959,455 to Ciarletta et al; U.S. Pat. No. 4,999,291).
Semina et al. (Radiatsionnaya Biologiya Radioekologiya 33(3), 1993; WO 8906134) have shown that the levorotary (L) enantiomer of the dipeptide H-Glu-Trp-OH acts as an immunostimulant and can induce the proliferation of cells. As such, these dipeptides are useful in reconstituting hemopoietic and immune cells after chemotherapy or irradiation therapy.